1. Field of the Invention
The present invention relates to a golf club. More specifically, the present invention relates to a golf club with an increased high repulsion area and an increased repulsion effect.
2. Description of the Invention
Various improvements are applied to a golf club in order to increase a traveling distance or so that a stable strike can be achieved. Particularly, the traveling distance using a driver club directly influences the score, so the traveling distance is increased if scope of a striking point on its head is enlarged, which is advantageous. The striking surface of the head is called “club face”, and a user usually uses a striking point called “sweet area” within the club face to strike a ball.
The striking point called “sweet area” is located adjacent to a center of gravity of the head, and is an area in which a traveling distance can be obtained most. Recently, there has been commonly used a golf club having an enlarged dimension of the driver head and thereby having an enlarged sweet area so as to realize an easy strike. Therefore, although this golf club has the advantages of resulting in less missed shots, that the struck ball does not curve, the traveling distance can be increased, and the like, the center of gravity is located at the upper side due to the enlarged dimension of the head, whereby the tendency for the sweet area to be moved to the crown side is inevitable.
For this reason, in order to obtain a traveling distance by maximizing the repulsive force that the head has, normally a ball has to be struck on the sweet area on the upper side from the center of the club face. For example, in a head (against) wind, if the ball is struck in the usual manner, the ball will have to fly against the wind, resulting in a failure to get the desired ball traveling distance, thus golfers usually strike the ball so as to produce a low ball trajectory because. In this case, the striking point is in a lower area of the club face. This, however, results in a decrease of the repulsive force and the ball traveling distance becomes less than that obtained by striking on the sweet area.
Because the center of gravity is located at the upper side of the club face, as mentioned above, that is, because the sweet area, which is a high-repulsion area, is in the vicinity of the center of gravity, if the striking point is off this area, repulsive force is reduced. Under these circumstances, various methods have been suggested to obtain a repulsive force comparable to that obtained at the conventional sweet area even at a lower point of the club face, thereby resolving the above problems. For example, as a method to increase the repulsive force, there is disclosed a golf club in which a certain area of the club face is specified and a restitution coefficient is set to minimize the decrease in ball traveling distance even at the time of offset strike (see Japanese Patent Application Laid-open No. 2002-17912, for example).
Furthermore, as a method of lowering the center of gravity and consequently increasing the repulsive force at the lower point of the club face, there is disclosed a method wherein a weight portion is provided in the lower part of the club head or the lower part is enlarged (see Japanese Patent Application Laid-open No. 2002-17908, for example). Moreover, a golf club, which has a configuration in which the club face portion is bended in a balanced manner, or other golf clubs are known (see Japanese Patent Application Laid-open No. H11-114102, for example). Also, the same applicant has been suggested a golf club in which the sole is improved so that the ball traveling distance of is not decreased even if the ball is struck at the lower part of the sweet area.
In addition, there is disclosed a technique for forming a hollow golf club head by combining a plurality of metal shells (see Japanese Patent Application Laid-open No. 2001-170225, for example), or a technique for forming a configuration in which a reinforcing member is provided as another body on the inner wall of the forward edge of the crown shell (see Japanese Patent Application Laid-open No. 2002-126134, for example). As above, techniques for producing a golf club by welding different metals are known.
As has been stated above, various methods have been devised to increase the ball traveling distance in a golf club. However, the proposed methods are still not satisfying. There is still room for improvement, particularly in terms of enlarging the sweet area. Conditions are restricted particularly in terms of producing a golf club, but it is desired to develop a golf club in which a ball traveling distance can be increased even when striking the ball in a normal fashion in such restricted conditions. In the past, some techniques were exercised, such that various modifications were applied to the body portion, or a weight portion was provided partially. However, these techniques have drawbacks in certainty, so they were not all necessarily satisfying since a slight adjustment had to be made in production of such golf clubs.
As described in the abovementioned patent applications disclosed as the prior art, the configuration for applying balanced bending on the club face portion and the crown portion is not also designed to improve a repulsion effect securely and stably in the lower part of the club face portion by enlarging the sweet area. Further, the method for providing a weight portion has some effects but also has a limit in the recent trend of enlarging the head part. In other words, there is generated a new problem that enlarging the head part by adding a weight portion will result in increasing the weight of the club head. The golf industry is a world where tradition is valued originally.
Substantial changes in the configuration, weight, etc., of the club head from those of the conventional one require users to change their golf swing and so forth, which may cause the swing rhythm to be destroyed. Even if an epoch-making golf club is developed, it will take a long time for the new golf club to become established in actual practice. Therefore, in terms of golf club appearance, it is ideal to develop a golf club which is improved in function to satisfy golfers, without substantially changing the configuration of the presently established golf clubs.
Also, the above patent applications disclose a configuration of a golf club in which the material of the head is changed. In this configuration applied in the golf club of the prior art, different type of metals, such as pure titan and a titanium alloy are applied for each part in the hosel part, or different types of metals are welded and joined as the reinforcing member. Therefore, this configuration is different from that of the present invention in which different types of metals are integrated in the same parts, so the objects of the aforementioned configuration are different from those of the present invention, and is not involved in the technique for enlarging a high repulsion area.
An ideal form of golf club does not exist in the actual situation. Therefore, it is desired to develop a golf club capable of enlarging the repulsion area and increasing the ball traveling distance stably without making substantial changes in the conventional shape.